U.S. patent number 5,593,941 [Application Number 08/363,827] was granted by the patent office on 1997-01-14 for process for production of thermally transferred image-receptive sheet.
This patent grant is currently assigned to Dynic Corporation. Invention is credited to Hiroshi Fukuhara, Hiromoto Kato.
United States Patent |
5,593,941 |
Kato , et al. |
January 14, 1997 |
Process for production of thermally transferred image-receptive
sheet
Abstract
There is disclosed a process for production of a process for
production of a thermally transferred image-receptive sheet which
comprises: (a) coating a coating composition containing nylon,
methanol and calcium chloride onto a woven fabric substrate, (b)
dipping the coated substrate into water to solidify a coated layer
and leach out methanol and calcium chloride, wherein a microporous
surface layer is formed so that the bottom of woven fabric is just
filled up, (c) drying the dipped substrate, and (d) furnishing the
dried substrate to obtain a final product, wherein a cover factor
of woven fabric in the final product is not lower than 1700 and a
ratio of cover factor of woven fabric immediately after coating
relative to that of the final product is 0.97 to 1.03.
Inventors: |
Kato; Hiromoto (Omihachiman,
JP), Fukuhara; Hiroshi (Hikone, JP) |
Assignee: |
Dynic Corporation (Kyoto,
JP)
|
Family
ID: |
26548391 |
Appl.
No.: |
08/363,827 |
Filed: |
December 27, 1994 |
Foreign Application Priority Data
|
|
|
|
|
Dec 28, 1993 [JP] |
|
|
5-335100 |
Nov 1, 1994 [JP] |
|
|
6-268615 |
|
Current U.S.
Class: |
503/227; 427/152;
427/355; 428/373; 428/401; 428/475.2; 428/475.5; 428/913; 428/914;
442/128; 442/164; 442/168; 442/60; 442/77 |
Current CPC
Class: |
B41M
5/52 (20130101); D06N 3/0052 (20130101); D06N
3/125 (20130101); D06P 5/003 (20130101); D06P
5/005 (20130101); Y10T 428/31739 (20150401); Y10T
442/2566 (20150401); Y10T 442/2861 (20150401); Y10T
442/2008 (20150401); Y10T 428/31736 (20150401); Y10T
442/2148 (20150401); Y10T 442/2893 (20150401); Y10T
428/298 (20150115); Y10T 428/2929 (20150115); Y10S
428/913 (20130101); Y10S 428/914 (20130101) |
Current International
Class: |
B41M
5/52 (20060101); B41M 5/50 (20060101); D06P
5/28 (20060101); D06N 3/12 (20060101); D06P
5/24 (20060101); D06N 3/00 (20060101); B41M
005/035 (); B41M 005/38 () |
Field of
Search: |
;427/152,355
;503/201,227 ;8/471
;428/195,286,287,475.2,475.5,480,913,914,373,401 |
Foreign Patent Documents
Primary Examiner: Hess; Bruce H.
Attorney, Agent or Firm: Jacobson, Price, Holman &
Stern, PLLC
Claims
What is claimed is:
1. A process for production of a thermally transferred
image-receptive sheet which comprises:
(a) coating a coating composition, containing nylon, methanol and
calcium chloride, onto a woven fabric substrate to obtain a coated
layer,
(b) dipping the thus-coated substrate into water to solidify the
coated layer formed in step (a) and leach out methanol and calcium
chloride, wherein a microporous surface layer is formed so that the
bottom of woven fabric is just filled up,
(c) drying the thus-dipped substrate, and
(d) furnishing the thus-dried substrate to obtain a final product,
wherein a cover factor of woven fabric in the final product is not
lower than 1700 and a ratio of cover factor of woven fabric
immediately after coating relative to that of the final product is
from 0.97 to 1.03.
2. A process according to claim 1, wherein the substrate is nylon
50-150 denier taffeta, polyester 30-150 denier taffeta or
polyester/nylon 30-150 denier taffeta core-sheath fiber woven
fabric, provided that when the substrate is polyester/nylon 30-150
denier taffeta core-sheath fiber woven fabric, the core fiber is
polyester.
3. The process according to claim 1, wherein the substrate is woven
fabric composed of filament yarns which are made of synthetic
fiber(s) other than nylon and polyester fiber and which have a
thickness of from 30 to 210 denier.
4. A thermally imaged image-receptive sheet comprising a) a woven
fabric substrate, b) a coating of microporous receiving material
and c) a thermally transferred image, wherein said sheet has a
cover factor which is not lower than 1700 and a ratio of cover
factor of woven fabric immediately after coating relative to that
of the final product of from 0.97 to 1.03.
Description
FIELD OF THE INVENTION
The present invention relates to a process for production of a
thermally transferred image-receptive sheet having improved
smoothness, and excellent cushioning properties, thermal
shapeability, resistance to solvents and resistance to washing.
BACKGROUND OF THE INVENTION
A thermally transferred image-receptive sheet used for thermal
transfer printing utilizing thermal transfer imaging or sublimation
transfer imaging requires clarity of the image. Important factors
in the clarity are smoothness and cushioning properties of the
surface of the image-receptive sheet.
On the other hand, from a viewpoint of handling, such as outdoor
use and the like, the image-receptive sheet requires strength,
resistance to folding, permanence properties and resistance to
water in some cases.
As a thermally transferred image-receptive sheet possessing
simultaneously smoothness, cushioning properties and strength,
there have been thermally transferred image-receptive sheets
wherein a polyamide or polyurethane microporous layer is provided
on a substrate, such as woven fabric and nonwoven fabric. These
types of thermally transferred image-receptive sheets have been
generally produced by coating a nylon coating composition
containing calcium chloride, methanol and nylon as a main component
or a polyurethane coating composition containing dimethylformamide
and polyurethane as a main component on a substrate, dipping the
coated substrate to form a nylon or polyurethane microporous layer
while leaching out the solvent and the like (for example, see JP-A
03-021487).
In such prior art, the coated substrate was dipped into water,
dried and furnished. In the furnishing step, regarding a cover
factor of woven fabric, a ratio of a cover factor thereof
immediately after coating relative to that of a final product
(referred to as "a cover factor ratio" hereinafter) was relatively
large (a cover factor ratio was above 1.03). Alternatively, another
attempt was tried by carrying out such furnishing step, followed by
a calendering step.
On the other hand, there has been a demand for high clarity of the
image. In order to respond to this demand, smoothness of a
thermally transferred image-receptive sheet obtained by a process
wherein a relatively large cover factor or a roll method
(calendering method) is used is required to be further
improved.
OBJECT OF THE INVENTION
The main object of the present invention is to provide a process
which can further improve smoothness of a thermally transferred
image-receptive sheet.
This object as well as other objects and advantages of the present
invention will become apparent to those skilled in the art from the
following description with reference to the accompanying
drawings.
SUMMARY OF THE INVENTION
In view of the above circumstances, the present inventors studied
intensively and, as the result, found that a thermally transferred
image-receptive sheet having improved smoothness can be
unexpectedly obtained by forming a microporous layer on the surface
of woven fabric to such an extent that the bottom of woven fabric
is just filled up.
That is, the present invention provides a process for production of
a thermally transferred image-receptive sheet which comprises:
(a) coating a coating composition containing nylon, methanol and
calcium chloride onto a woven fabric substrate,
(b) dipping the coated substrate into water to solidify a coated
layer and leach out methanol and calcium chloride, wherein a
microporous surface layer is formed so that the bottom of woven
fabric is just filled up,
(c) drying the dipped substrate, and
(d) furnishing the dried substrate to obtain a final product,
wherein a cover factor of woven fabric in the final product is not
lower than 1700 and a ratio of cover factor of woven fabric
immediately after coating relative to that of the final product is
0.97 to 1.03.
BRIEF EXPLANATION OF DRAWINGS
FIG. 1 is a perspective view showing an apparatus for producing a
thermally transferred image-receptive sheet according to the
present process.
FIG. 2 is a cross sectional view schematically showing flattened
filament yarns and non-twisted yarns in woven fabric.
FIG. 3 is a partial cross sectional view schematically showing the
internal structure of a thermally transferred image-receptive sheet
produced according to the present process.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIG. 1, a process of the present invention comprises
fundamentally steps: coating step, coated layer solidifying step,
drying step and furnishing step.
Firstly, woven fabric is used as a substrate to be delivered to
coating step. Preferable woven fabric materials are synthetic
fibers, such as polyester and nylon, from a viewpoint of resistance
to water, resistance to folding and the like. Alternatively, other
synthetic fibers, such as acrylic, vinylon, vinylidene fiber and
the like, may be used. As a yarn, filament yarn is preferable
wherein a component single yarn is fine. Since monofilament, thick
yarn and twisted yarn have inferior smoothness, they are not
preferable. Therefore, non-twisted yarn is preferable. From a
viewpoint of material and thickness, nylon 30-210.sup.d, preferably
50-110.sup.d taffeta; polyester 30-150.sup.d, preferably
50-110.sup.d taffeta and 30-150.sup.d, preferably 50-110.sup.d
core-sheath fiber woven fabric (polyester/nylon) (core fiber;
polyester) are particularly preferable. The above synthetic fibers
other than nylon and polyester fiber can be used as woven fabric in
a substrate, as far as they are composed of filament yarns and
thickness thereof is 30-210.sup.d.
In addition, polyester taffeta and other synthetic fibers other
than nylon fiber (sheath fiber is other than nylon fiber, in the
case of core-sheath fiber) are preferably impregnated with a resin,
such as nylon, urethane, EVA and the like, in order to improve
adhesion between a substrate and a nylon microporous layer formed
thereon.
In coating step, a substrate of continuous length 1 is first
delivered therein using, for example, roll method or yard-fold
method.
In coating step, a nylon coating composition is coated onto the
delivered substrate.
Examples of nylon used in the nylon coating composition are nylon
6, nylon 6--6, nylon 8 and the like. From a viewpoint of deforming
and resilient properties of a microporous layer formed in later
step by setting pressure, surface tackiness and like, nylon 6 and
nylon 6--6 are preferably used. A nylon coating composition
contains 5 to 50% by weight, preferably 10 to 28% by weight of
nylon. Further, a nylon coating composition contains methanol and
calcium chloride for forming a microporous layer. An amount of
methanol to be contained is 40 to 80% by weight, preferably 55 to
60% by weight on the basis of the weight of total weight of a nylon
coating composition. An amount of calcium chloride to be contained
is 15 to 35% by weight, preferably 20 to 29% by weight on the basis
of the total weight of a nylon coating composition.
As other components, a nylon coating composition may contain a
filler, such as clay, silica, calcium carbonate, talc and the like;
a plasticizer such as sulfonamides, aromatic oxycompounds, carbamic
ester, DOA and the like; an antistatic agent, such as amine,
polyoxyethylene ether and the like, from a viewpoint of workability
in the process of production or final utility of a printed
image-receptive sheet.
A nylon coating composition is prepared by mixing the above
components. The viscosity of a nylon coating composition is
preferably 500 to 2000 cps at 40.degree. C. by measurement using a
B type viscometer, from a viewpoint of workability upon
coating.
The composition thus prepared is coated onto a substrate. Coating
is carried out onto one side or two sides of the substrate
depending upon the intended utility. FIG. 1 show an embodiment
wherein a composition 3 is coated onto one side of the substrate
using a doctor knife 2 and an on-roll method.
Besides on-roll method, examples of a coating method are floating
method, blanket method, slit-coat method, reverse-coat method,
cast-coat method. For obtaining an image-receptive sheet having
excellent smoothness, on-roll method, floating method and blanket
method are effective.
An amount to be coated is such that the bottom 12 of woven fabric
is just filled up so as to form a coated layer. As used herein, the
description "the bottom of woven fabric is just filled up" refers
to the situation where the top 11 of woven fabric is extremely near
zero and the surface of coated layer is flat (see FIG. 3). The
reason why such the amount to be coated is selected is as follows:
As the thickness is growing larger starting from the above just
filled up situation, the feeling of a woven fabric is lost
gradually and the surface peel strength (picking test using Denison
wax, pressure sensitive adhesive tape and the like) of the coated
layer is decreased. Therefore, an amount to be coated is limited to
some extent and, when a doctor knife is used, coating is carried
out by contacting a tip of the knife with woven fabric so that the
knife scrapes the crest of fiber in woven fabric.
Usually, coating is carried out once to four times. For example,
the particular amount to be coated is 15 to 30 g/m.sup.2 when a
substrate is nylon taffeta 70 d (total density 210/inch.sup.2).
In addition, coating is usually carried out while tension is
applied to a substrate in the longitudinal direction (delivering
direction of a substrate) at 0.5 to 1.5 kg/cm.
In next coated layer solidifying step, the coated substrate is
delivered to a water cistern 4, and dipped into water having pH of
3 to 8 to leach out calcium and methanol. For example, when
CaCO.sub.3 is used as a filler, hydrochloric acid is added thereto
to adjust pH to acidic in order to remove CaCO.sub.3 by
decomposition.
Such leaching out forms a nylon microporous layer on a substrate.
Upon this, a part of a substrate is dissolved, which results in
incorporation of a substrate and a microporous layer. As used
herein, the term "microporous" refers to a layer possessing pores
having the diameter of about 0.1 to 5 .mu.m.
In order to obtain excellent smoothness, solidification (gelation)
is successively caused starting from the surface of coated layer.
Successive solidification occurs by dipping into water as described
above. Alternatively, only placing water on a substrate causes
successive solidification. Upon this, since the solvent contained
in a coating composition is successively leached out and the
leached out solvent is displaced by water, volume reduction is not
or hardly caused in a formed nylon microporous layer. In this
respect, volume reduction is caused when a coating composition
containing a solvent is heated. The present process is different
from the heating method. Thus, volume reduction of a microporous
layer is hardly caused in solidifying step in the present process,
and the situation where the bottom of woven fabric is just filled
up is maintained also in a final product.
Drying is carried out using a drier 5. A temperature for drying is
usually at 100.degree. to 150.degree. C. and a time for drying is
about 180 to 10 seconds depending upon the temperature for drying.
The drying method includes and is not limited to nontouch-drying
method, cylinder-drying method, tenter-drying method,
floating-drying method, arch-drying method and the like.
In furnishing step, furnishing is carried out so that a cover
factor of a final product becomes not lower than 1700, preferably
not lower than 2000 and a cover factor ratio becomes 1.0 to
1.03.
A cover factor (K) is calculated according to the following
equation:
wherein m is the diameter of yarn and p is the distance between
yarns. For simplicity, a cover factor is calculated according to
the following equation:
wherein n is density (/inch.sup.2), N is count of yarn. In the case
of filament yarn, K=n.sqroot.D, wherein n is density, D is denier
value, wherein D=9000 .times. W/L, wherein W is weight and L is
length.
When woven fabric composed of filament yarn or non-twisted yarn
(naturally twisted yarn) is used, a cross section of a yarn is out
of round or flattened and, thereby, a cover factor becomes
substantially larger than that obtained by the above equation
(because the diameter of a yarn becomes larger due to flattening).
In such the case, the following equation is used:
wherein k is correction factor and is obtained by dividing the
major axis shown in FIG. 2 by the corresponding diameter if a cross
section of the same yarn is circle. Correction factor (k) is
usually within a range of 1.3 to 1.8 and a cover factor (K) is
calculated by selecting correction factor from the above range.
In the previous furnishing step where a cover factor ratio was
relatively large (above 1.03), the warps were moved by furnishing
treatment and, as the result, protuberances are formed. This is
considered to be the reason why surface smoothness of a microporous
layer after furnishing was. insufficient in the case of the
previous furnishing treatment.
It has been now found that smaller cover factor ratio prevents the
warps of a substrate from moving and, thereby, surface smoothness
is improved.
In the furnishing step, furnishing is carried out by grasping a
substrate with a tenter 6. Examples of the tenter are pin tenter,
clip tenter and roller setter. In addition, the roller setter must
be equipped with a trimming instrument.
A temperature in the furnishing step is generally higher to some
extent than that in the above drying step.
One embodiment of a cover factor in the present process is shown
together with that in the previous process.
______________________________________ Immediately Furnishing Cover
factor after coating treatment ratio
______________________________________ Previous process 3130 3009
1.04 Present process 3130 3101 1.01
______________________________________
Thus, an image-receptive sheet 7 (embodiment of two sides coating)
obtained by the present process comprises a substrate layer 8 and a
microporous layer (image-receptive layer) 9 as schematically shown
in a cross sectional view in FIG. 3. In the sheet, nylon is present
in the gap between yarns 10 and, as the result, a microporous layer
9 is incorporated with a substrate. And small cover factor ratio in
furnishing step affords particularly excellent smoothness.
Next, the image-receptive sheets obtained by the present process
were evaluated as follows:
Five kinds of substrates shown in Table 1: (i) nylon taffeta
210/inch.sup.2, 70 d (ii) polyester taffeta 190/inch.sup.2, 75 d
(iii) spun yarn woven fabric 40 counts, (iv) polyester/nylon
core-sheath taffeta 190/inch.sup.2, 50 d (v) polyester/nylon
core-sheath taffeta 180/inch.sup.2, 75 d) were furnished at a
relatively large cover factor ratio (cover factor ratio=1.07) (in
Table 1, "large") after drying step, respectively, or these
furnished substrates were further subjected to rolling
(calendering) (cover factor ratio=1.04) (in Table 1, "roll"),
respectively. Separately, the above five kinds of substrates were
furnished at a relatively small cover factor ratio (cover factor
ratio=1.01) (in Table 1, "small") after drying step. Smoothness of
these substrates were determined.
Evaluation was carried out by measuring a time for which a constant
amount of air has flown through a gap between the flat sheet and
the uneven surface of a sample using Oken-type smoothness tester
(Model KY-5) (manufactured by Asahiseiko K. K.). In the measured
time, when the time is longer, smoothness is higher. Form a
practical point of view, smoothness required for the
image-receptive sheet is not lower than 200 seconds.
Test samples and results are shown in Table 1.
TABLE 1 ______________________________________ Furnishing method
Woven fabric density thickness large.sup.1 roll.sup.2 small.sup.3
______________________________________ Nylon taffeta 210/inch.sup.2
70d 90s 320s 580s Polyester taffeta 190/inch.sup.2 75d 60s 290s
550s Spun woven fabric 130/inch.sup.2 40 counts 4s 14s 10s
Polyester/Nylon 190/inch.sup.2 50d 40s 59s 166s core-sheath taffeta
Polyester/Nylon 190/inch.sup.2 75d 52s 99s 220s core-sheath taffeta
______________________________________ .sup.1 ; previous process,
.sup.2 ; previous process, .sup.3 ; present process
As shown in Table 1, when a cover factor ratio is relatively large
according to the previous method, smoothness is lower. In addition,
a microporous layer may be broken in the case of a rolling method,
which results in lower smoothness. On the other hand, when a cover
factor ratio is small according to the present process, smoothness
is improved.
A microporous layer of a thermally transferred image-receptive
sheet obtained by the present process is composed of nylon which
can receive a sublimating dye and has excellent smoothness as
described above. Therefore, such thermally transferred
image-receptive sheet is an excellent sublimation transfer-type
image-receptive sheet which can give the clear image.
In addition, a microporous layer of the thermally transferred
image-receptive sheet obtained by the present process can receive a
heat meltable ink sufficiently. In particular, in the case where a
sheet after printing requires resistance to washing, such thermally
transferred image-receptive sheet can be appropriately used for
printing by thermal transfer using a resin-type heat meltable ink
having high fastness.
One example of the formulation of the resin-type heat meltable ink
is as follows:
______________________________________ Nylon 6/66/12 nylon 5 weight
parts Carbon black 5 weight parts Methanol 45 weight parts Toluene
45 weight parts ______________________________________
The present process can be appropriately applied to production of
thermally transferred image-receptive sheets which are printed and
used for display label, care label, brand label, industrial label
(production control label, laundry control label).
EXAMPLE
The following Examples and Comparative Examples further illustrate
the present invention in detail but are not to be construed to
limit the scope thereof. Part means part by weight.
Example 1
10 Parts of nylon staple, a solution of 12 parts of calcium
chloride and 20 parts of methanol, and filler and other additives
were mixed, the mixture was stirred at a temperature of not lower
than 70.degree. C. to obtain a nylon coating composition. The
viscosity of the nylon coating composition was measured to be 9000
cps at 40.degree. C. by a B type viscometer.
The above nylon coating composition was coated onto nylon taffeta
(weight 63 g/m.sup.2) composed of warps and wefts (single yarn 3 d;
70 d composed of filament count 24 f), 125 cm in width and
210/inch.sup.2 in total density, using a doctor knife according to
an on-roll method, while applying tension thereto. Coating
conditions were such that a tip of a doctor knife was held
contacted with woven fabric. An amount to be coated (wet) was 23
g/m.sup.2.
The coated woven fabric was dipped into water to leach out methanol
and calcium chloride contained in the composition and solidify the
coated layer. After solidification of layer, the woven fabric was
dried at 100.degree. to 120 .degree. C. for 30 seconds.
The dried woven fabric was furnished at 180.degree. C. for 10
seconds using a pin tenter to obtain a sheet having smoothness of
500 seconds and cushioning properties. Weight of the sheet was 72
g/m.sup.2, amount of coated resin was 5 g/m.sup.2 and the thickness
of the sheet was 111 .mu.m. A cover factor of a final product was
218.times..sqroot.70.times.1.7 (correction factor)=3101, a cover
factor immediately after coating was
220.times..sqroot.70.times.1.7=3129, and a cover factor ratio was
1.01.
Comparative Example 1
10 Parts of nylon staple, a solution of 12 parts of calcium
chloride and 20 parts of methanol, filler and other additives were
mixed, and the mixture was stirred at a temperature of not lower
than 70.degree. C. to obtain a nylon coating composition. The
viscosity of the nylon coating composition was measured to be 9000
cps at 40.degree. C. using a B type viscometer.
The above nylon coating composition was coated onto nylon taffeta
(weight 63 g/m.sup.2) composed of warps and wefts (single yarn 3d;
70d composed of filament count 24 f), 125 cm in width and
210/inch.sup.2 in total density, using a doctor knife according to
an on-roll method, while applying tension thereto. Coating
conditions were such that a tip of a doctor knife was held
contacted with woven fabric. An amount to be coated (wet) was 23
g/m.sup.2.
The coated woven fabric was dipped into water to leach out methanol
and calcium chloride contained in the composition and solidify the
coated layer. After solidification of the coated layer, the woven
fabric was dried at 100.degree. to 120.degree. C. for 30
seconds.
The dried woven fabric was furnished at 180.degree. C. for 10
seconds using a pin tenter to obtain a sheet having smoothness of
90 seconds and cushioning properties. Smoothness of this sheet is
lower than that of Example 1. Weight of the sheet was 68 g/m.sup.2,
amount of coated resin was 5 g/m.sup.2, and the thickness of the
sheet was 110 .mu.m. A cover factor of a final product was
212.times..sqroot.70.times.1.7 (correction factor)=3015, a cover
factor immediately after coating was
221.times..sqroot.70.times.1.7=3143, and a cover factor ratio was
1.04.
Example 2
10 Parts of nylon staple, a solution of 12 parts of calcium
chloride and 20 parts of methanol, and filler and other additives
were mixed, the mixture was stirred at a temperature of not lower
than 70.degree. C. to obtain a nylon coating composition. The
viscosity of the nylon coating composition was measured to be 9000
cps at 40.degree. C. by a B type viscometer.
The above nylon coating composition was coated onto polyester
taffeta (weight 65 g/m.sup.2) composed of warps and wefts, 75d,
190/inch.sup.2 in total density, 129 cm in width, using a doctor
knife according to an on-roll method, while applying tension
thereto. Coating conditions were such that a tip of a doctor knife
was held contacted with woven fabric. An amount to be coated (wet)
was 46 g/m.sup.2.
The coated woven fabric was dipped into water to leach out methanol
and calcium chloride contained in the composition and solidify the
coated layer. After solidification of the coated layer, the woven
fabric was dried at 100.degree. to 120.degree. C. for 30
seconds.
The dried woven fabric was furnished at 180.degree. C. for 10
seconds using a pin tenter to obtain a sheet having smoothness of
550 seconds and good cushioning properties. Weight of the sheet was
79 g/m.sup.2, the coated amount of resin was 11 g/m.sup.2 and the
thickness of the sheet was 100 .mu.m. A cover factor of a final
product was 205.times..sqroot.70.times.1.7 (correction
factor)=2915, a cover factor immediately after coating was
207.times..sqroot.70.times.1.7=2944, and a cover factor ratio was
1.01.
* * * * *